class_docstr: Unit test class for testing scikit-learn converter.
class_docstr_tok: ["Unit","test","class","for","testing","scikit-learn","converter","."]
code: def test_conversion_bad_inputs(self):
      # Error on converting an untrained model
      with self.assertRaises(Exception):
          model = GradientBoostingRegressor()
          spec = skl_converter.convert(model, "data", "out")
  
      # Check the expected class during conversion.
      with self.assertRaises(Exception):
          model = OneHotEncoder()
          spec = skl_converter.convert(model, "data", "out")
  
file_path: coremltools/coremltools/test/xgboost_tests/test_boosted_trees_regression.py
imports: import json
  import tempfile
  import unittest
  from coremltools._deps import _HAS_SKLEARN, _HAS_XGBOOST
  from coremltools.models.utils import _macos_version
label_desc: Use image node_id 3 for calling the GradientBoostingRegressorScikitTest obj's underlying member method code with example usage: obj.test_conversion_bad_inputs() without return types